Antenna mounting fixture with loading coil



Jan. 19, 1965 J. B. ROLL 3,166,751

ANTENNA MOUNTING FIXTURE WITH LOADING COIL Filed Sept. 27, 1962 l 2 Sheets-Sheet 1 l INVENTOR i5/w .8. Ro/ L ATTORNEYS Jan. 19, 1965 J'. B. RoLl.

ANTENNA MOUNTING FIXTURE WITH LOADING con.

Filed Sept. 27. 1962 2 Sheets-Sheet 2 INVENTOR JEH/v3 POL/ BY a ha UnitedStates Patent Olice 3,166,751 Patented Jan. 19, 1965 3,166,751 ANTENNA MOUNTING FIXTURE WITH LOADING CGIL John B. Roll, Plainfield, NJ., assignor to DPZ Corporation, New York, N Y., a corporation of New York Filed Sept. 27, 1962, Ser. No. 226,611 7 Claims. (Cl. 343-749) This invention relates to radio antennae and more particularly to antennae of relatively simple, sturdy construction having a fixed inductance coil incorporated in the circuit.

It'is an object of the invention to provide a simple, strong antenna construction.

It is a further object to provide an antenna construction in which various components are vpermanently united by insulating material cast in place around them.

It is still a further object to produce an antenna structure incorporating avremovable inductance coil assembly allowing the` use of several such coils of varying inductance depending upon the frequency of the signal being received, Y

.Still further objects of the invention will appear from the following description, in whichv FIG. l is a partial cross sectional view of an antenna structure during assembly of its parts;

FIG. 2 is a partial cross sectional view of an assembled antenna structure; l v

FIG. 3 is a partial view of an assembled antenna structure;

FIG. 4 is an enlarged cross sectional view on plane 4 4 of FIG. 3;

FIG. 5 is a partial cross sectional view corresponding to that in FIG. 4 of lan alternate antenna construction;

FIG. 6 is a perspective view of a short-#circuiting sleeve for 4use in the construction of FIG'. 5 ;l

FIG. v7 is apview lcorresponding to that of FIG. 5 showing an alternate coil in place; and

FIG. 8 is a perspective View or .the alternate coil of FIG. 7.

FIG. l shows a portion'of a coaxial cable 10 comprised of an inner conductor 11, an insulation layer 12, and woven wire shielding braid 13. During assembly the cable is passed through central bore 14 in base mounting screw 15 ,and end 16 of the shielding braid is spread away from the insulation layer to form the flared opening 17. Tapered'ferrule wedge 18 is passed down over the upper end of the yinsulation layer, which makes a sliding fit with axial hole 19 therein.

The coaxial cable and the base mounting screw are then locked together by forcing the errule wedge downward into the central bore 14 of the base mounting screw to the position shown in` FIG. 2. The central bore is comprised of a cylindrical segment 2d and a flared segment 21, the former adapted to loosely clasp the coaxial cable and the latter, in conjunction with ferrule wedge 18, to grasp tightly the shielding braid. This construction holds the coaxial cable securely without the necessity of knotting it, pinching the insulation, or putting stress on the inner conductor 11.

The assembly of FIG. 2 is incorporated into the iinished structure of FIGS. 3 and 4 by casting molded base 22 around head 23 of the base mounting screw. Grooves 24 in head 23 give the cast material a good grip on the head. Since the molded base serves both as an insulator and as a load-bearing mechanical component it has been found that this element is best made of a high strength plastic such as nylon. The upper end 25 of the molded basegrips antenna connection socket 26 which bears peripheral grooves 27 to insure a permanent connection. Bore 28 in socket 26 makes a force fit with the bottom end 29 of a conventional tubular-'antenna rod 30, which may extend upward to any convenient height.

Prior to the casting step, the antenna connection socket 26 and the base mounting screw 1S are placed so as to project into the cavity of a suitable mold (not shown). The end 31 of the inner conductor is bent to one side and extends into the wall of the mold cavity, so that a short length projects from the molded base. Connection between the antenna rod 30 and the inner conductor 11 is effected through an inductance coil comprised of inductance wire 32, wrapped in a helix around the molded base. One end of the inductance wire is provided with a loop 33 soldered thereto. The loop is maintained in electrical lcontact with end 31 of the inner conductor by means of lower screw 34 which is threaded into tapped hole 35 in the molded base. The inner conductor is wrapped around the lower screw, which presses it against the loop in the inductance wire when the screw is tightened.

The helical turns of inductance wire may be kept in y place on the molded base by suitable varnish or glue. The upper end 36 of the inductance wire is wrapped around upper screw 37, which passes through hole 3S in the molded base and is threaded into a tapped hole 39 in the antenna connection socket 26.

In use the antenna is fastened to a suitable bracket 4i) by passing the base mounting screw through a mounting hole 41 in the bracket and tightening nut 42 on the threads 43 of the mounting screw.

The antenna described above has an inductance coil which is an integral part of of the rest of the device. It is often desired to change the inductance of the coil depending on the size of the antenna rod and the frequency of the signals being received. FIGS. 5-8 show an alter- `nate construction allowing such changes, as well as illustrating variations in the design of other components. In FIG. 5 lis shown base mounting screw 44 united with a coaxial cable 45 in an assembly identical with that of FIG. 2. End 46 of the inner conductor 47 is soldered into central bore 48 of metal barrel 49. The molded base 50 is then cast about the components just described, as well as around antenna connection socket 6d which is similar to antenna connection socket 26 of FIG. 4.

Y In the embodiment -of FIGS. 5-8 a cylindrical sleeve of insulating material is provided to slip loosely over the molded base 50. The cylindrical sleeve is held in place by a lower screw 52 which passes through a hole 53 in the sleeve and a hole 54 in the molded base and screws into tapped hole 55 in metal barrel 49. Upper screw S6 passes through hole 57 in the ycylindrical sleeve, hole 53 in the molded base, and into tapped hole 59 in antenna connection socket 60, the latter being similar in construction to antenna connection socket 26 of FIG. 4.

In FIGS. 5 and 6 sleeve 51 is equipped with a metal shunt 61 extending between the upper screw S6 and the lower screw S2. Thus, no inductance is put into the circuit by the sleeve. FIGS. 7 and 8 show a second sleeve 62 which may be slipped over molded base Sti in place of sleeve 51 when it is desired to add an inductance coil in series with the antenna. Sleeve 62 is provided with an induct'ance wire 63 Wound helically on its outer surface and held in place with varnish or glue. of the inductance wire are fastened to the sleeve by metal rivets 64 and 65 which have central holes through which the upper and lower screws pass. Y

FIGS. 5 and 7 showA a second type ofv antenna rod. Antenna rod 66 has a widened lower end 67, the central bore 68 of which ts over the outside of antenna connection socket di). The fit may be a force tit if a permanent connection is desired, or it may be a loose fit with a setscrew 69 holding the parts together.

The ends The antenna described is simple and rugged in its construction. The molded nylon base completely encloses and seals the open end of the coaxial cable and prevents loosening of the ferrule wedge 18. The inductance coil is exposedk so that the number of turns therein may be varied, either Vby changing a removable sleeve or by stripping off part of the inductance wire from the outside of the molded base and reconnecting the remainder.

The following is claimed:

1. An antenna structure comprising (a) a base mounting screw having a longitudinal central bore, a threaded shank, and a head;

(b) a coaxial cable passing upward through the central bore of the base mounting screw and havingan inner conductor, an insulating layer surrounding the inner conductor, and a shielding braid surrounding the insulating layer, the upper end of the inner conductor projecting beyond the head of the base mounting screw;

(c) a ferrule wedge having an axial hole, the insulating layer and the inner conductor of the coaxial cable passing upward through the axial hole and the ferrule wedge lying at least partly inside the shielding braid, said ferrule wedge forcing the shielding braid outward against the wall o'f the central bore of the base mounting screw and thus cooperating Vwith said wall to grip the shielding braid tightly;

(d) an antenna connection 'socket adapted to couple to an antennarod;

(e) a molded base of insulating material molded about and securely gripping the head of the base mounting screw and partially enclosing the upper end of the inner conductor, said molded base partially surrounding and securely gripping the antenna connection socket while maintaining said antenna connection socket out of direct electrical contact with said base mounting screw; and i (f) electrical connecting means for carrying current between the upper end of the inner conductor and the antenna connection socket.

2. The antenna structure of claim 1 wherein the'electrical connecting means comprises an inductance coil wound around the outside of the molded base.

3. The antenna structure of claim 1 wherein the elec- Y trical connecting means comprises a demountable sleeve adapted to surround the molded base and an inductance coil wound around said sleeve.

' 4. The antenna structure of claim 1 wherein the electrical connecting means comprises a demountable sleeve adapted to surround the molded base and a shunt mounted on said sleeve.

5. The antenna structure of claim 1 wherein the molded V base is formed of nylon.

6. An antenna structure comprising (a) a base mounting screw having a substantially cylindrical shank withexternal threads thereon, a head at one end of the shank, indentations on the head, and a central bore, said central bore being comprised of a cylindrical portion within the shank` and a tapered portion at least partially within the head, said tapered portion flaring outward; (b) a coaxial cable having anV inner conductor, an

insulating layer surrounding the inner conductor, and

a shielding braid surrounding the insulating layer, the upper end of the inner conductor extending past the upper ends of the insulating layer and shielding braid;

(c) a ferrule wedge having a cylindrical axial hole surrounding the insulating layer adjacent the upper end thereof and a tapered outer surface contacting the inner surface of the shielding braid adjacent the upper end thereof and forcing the shieldingV braid outward against the tapered portion of the central bore of the base mounting screw;

(d) an antenna connection socket having an axial bor and indentations in its outer surface; j

(e) an elongated plastic moldedl base of substantially 'circular cross section in a plane perpendicular to its longitudinal axis, the material in said base adjacent the lower end thereof surrounding and firmly gripping the vhead of lthe base mounting screw and the material in said base adjacent the upper end thereof surrounding and firmly gripping the surface of the antenna connection socket bearing the indentaf tions; andV y V (f) inductance wire coil surrounding the molded -base and having one end electrically connected to the inner conductor and the other end electrically connected to the antenna connection socket.

7. The antenna structure of claim 6 comprising a removable cylindrical sleevesurrounding thefmolded base and bearing on its outer Vsurface the inductance wire coil.

References Citedk in the le of this patent UNITED STATES PATENTS 1,673,458 Jones Q June.12, 1928 2,473,141 Friedberg June 14, 1949 2,481,823 Cejka -Sept. 13, 1949 2,482,567 Trowbridge Sept. 20, 1949 2,498,350 Walsh Feb. 2l, 1950 2,693,372 Ludwig et al. NOV. 2, 1954 2,771,604 Goldstein Nov. 20, 1956v 2,841,789 y Bassett n July 1, 1958 

1. AN ANTENNA STRUCTURE COMPRISING (A) A BASE MOUNTING SCREW HAVING A LONGITUDINAL CENTRAL BORE, A THREADED SHANK, AND A HEAD; (B) A COAXIAL CABLE PASSING UPWARD THROUGH THE CENTRAL BORE OF SAID BASE MOUNTING SCREW AND HAVING AN INNER CONDUCTOR, AN INSULATING LAYER SURROUNDING THE INNER CONDUCTOR, AND A SHIELDING BRAID SURROUNDING THE INSULATING LAYER, THE UPPER END OF THE INNER CONDUCTOR PROJECTING BEYOND THE HEAD OF THE HEAD MOUNTING SCREW; (C) A FERRULE WEDGE HAVING AN AXIAL HOLE, THE INSULATING LAYER AND THE INNER CONDUCTOR OF THE COAXIAL CABLE PASSING UPWARD THROUGH THE AXIAL HOLE AND THE FERRULE WEDGE LYING AT LEAST PARTLY INSIDE THE SHIELDING BRAID, SAID FERRULE WEDGE FORCING THE SHIELDING BRAID OUTWARD AGAINST THE WALL OF THE CENTRAL BORE OF THE BASE MOUNTING SCREW AND THUS COOPERATING WITH SAID WALL TO GRIP THE SHIELDING BRAID TIGHTLY; (D) AN ANTENNA CONNECTED SOCKET ADAPTED TO COUPLE TO AN ANTENNA ROD; (E) A MOLDED BASE OF INSULATING MATERIAL MOLDED ABOUT AND SECURELY GRIPPING THE HEAD OF THE BASE MOUNTING SCREW AND PARTIALLY ENCLOSING THE UPPER END OF THE INNER CONDUCTOR, SAID MOLDED BASE PARTIALLY SURROUNDING AND SECURELY GRIPPING THE ANTENNA CONNECTION SOCKET WHILE MAINTAINING SAID ANTENNA CONNECTION SOCKET OUT OF DIRECT ELECTRICAL CONTACT WITH SAID BASE MOUNTING SCREW; AND (F) ELECTRICAL CONNECTING MEANS FOR CARRYING CURRENT BETWEEN THE UPPER END OF THE INNER CONDUCTOR AND THE ANTENNA CONNECTION SOCKET. 